Since more than a decade hematoporphyrin and its derivatives /HpD/ serve as photosensitizers applied for detection and destruction of neoplasms in humans and animals. These compounds are injected intravenously and are translocated via active transport to various body organs. In healthy tissues they remain for a relatively short time, as they are metabolized and excreted, whereas in neoplastic tissues they are retained and remain there for several days on an unchanged level. This feature was utilized in the photodynamic method for the diagnosis and selective destruction of neoplastic tissues. Since all hematoporphyrin derivatives are sparingly soluble in water, preparation of their aqueous solutions was so far very troublesome.
In "Cancer Research", v.44, p. 1924,1984 /see also ibid, v. 45, p.635,1985/ a method for obtainment of hematoporphyrin preparations to be used for injections was reported. According to this method, hematoporphyrin derivatives are disolved in a NaOH solution, stirred for 1 h and adjusted to pH ca. 7.1 with 0.1N HCl. This is very inconvenient, since even slight exceeding of pH below 7.0 causes precipitation of the compound. The final solution is prepared by adding an appropriate amount of saline. The solution is sterilized and stored in sealed ampoules. These agueous solutions are unstable on account of the strong tendency of all hematoporphyrin derivatives for aggregation. According to the quoted paper, the solutions remain stable for ca. 3 months provided they are refrigerated /at &lt;20.degree. C./ in the dark.